JPS608973B2 - Process for producing basic aluminum chloride salt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a basic aluminum chloride salt, and more particularly to a method for producing a basic aluminum chloride flocculant using an amorphous carbonate radical-containing aluminum hydroxide as an intermediate.

Basic aluminum chloride salts are useful as flocculants,
Many proposals have been made regarding its manufacturing method.

A typical method is to dissolve aluminum hydroxide in hydrochloric acid, but ordinary aluminum hydroxide is generally difficult to dissolve in hydrochloric acid, and even if it dissolves in hydrochloric acid, the basic aluminum chloride salt solution produced is stable. The disadvantage is that it is lacking in The present inventors have found that when neutralizing a soluble aluminum salt in an aqueous medium containing an alkali carbonate so that the pH during the reaction is 6.5 to 9.8, CO
An amorphous carbonate-containing aluminum hydroxide having a molar ratio of 2/A-203 of 0.1 or more is formed, and this amorphous carbonate-containing aluminum hydroxide simply has excellent solubility in hydrochloric acid. Not only does it retain its excellent solubility even when left for a long period of time, so it can also be used as a flocculant.
The present invention has been achieved based on the discovery that there is no need to transport it in expensive liquid form, and that by melting it on site and supplying it in liquid form, it has significant advantages such as a significant reduction in transportation costs.

That is, according to the present invention, the pH during the reaction of soluble aluminum salt in an aqueous medium containing an alkali carbonate is 6.5 to 9.
．． 8 to produce an amorphous carbonate-containing aluminum hydroxide having a molar ratio of C02/A203 of 0.1 or more; By dissolving it in hydrochloric acid or a mixed acid of hydrochloric acid and sulfuric acid, the formula A2(〇H)X・C〆y-(S〇4)Z in the formula,
x, y, and z are: x y + Z = 6, x is a number from 2.7 to 5, and z is a number that satisfies a number from 0 to 0.65. A method of making a basic aluminum chloride salt is provided, comprising the steps of:

In the present invention, mineral acid salts of aluminum, such as aluminum sulfate, are preferably used as the soluble aluminum salt.

This raw material aluminum sulfate solution can be easily obtained by, for example, extracting montmorillonite group clay minerals such as acid clay, or other clay minerals such as calcined kaolin with sulfuric acid, and performing a purification or concentration treatment by means known per se. can get.
Among other types of soluble aluminum salts, mention may be made of alkaline aluminate solutions, which can be prepared from alumina raw materials such as bauxite using the Bayer method and JP-A No. 10790/1983. Produced by extraction as described. Soluble aluminum salts can be used alone or in combination of two or more, for example, a combination of aluminum sulfate solution and sodium aluminate can be used, as detailed later. According to the invention, the soluble aluminum salt is prepared in an aqueous medium containing an alkali carbonate at a pH of 6.5 to 9.8, preferably at a pH of 7.
to 9.5, and the molar ratio of C02/Aso203 is 0.
．． 1 or more, especially 0.2 or more amorphous carbonate radical-containing aluminum hydroxide (hereinafter sometimes simply referred to as an amorphous intermediate) is formed. When the soluble aluminum salt is a mineral acid salt, this neutralization can be carried out using an alkali.
Alternatively, a combination of an alkali carbonate and another alkali, such as an alkali hydroxide or an alkali aluminate, may be used. Further, when the raw material aluminum salt is an alkali aluminate, neutralization may be performed using mineral acids such as hydrochloric acid and sulfuric acid. It should be understood that, as described above, aluminum sulfate and an alkali aluminate may be mixed to perform neutralization by double decomposition. This neutralization reaction was carried out in an aqueous medium containing an alkali carbonate and as described in Section 6 above.
Working at a pH between 5 and 9.8 is extremely important in obtaining the amorphous carbonate intermediate.

That is, when neutralizing is carried out under conditions where the pH is lower than 6 or higher than 10, even if the aqueous medium contains alkali carbonate, the aluminum hydroxide produced will contain A.
It is difficult to contain 0.1 mol or more of carbonate radicals per 2031 mol of carbonate. Furthermore, aluminum hydroxide with a carbonate line content lower than the range specified in the present invention has lower solubility in hydrochloric acid than the amorphous carbonate intermediate according to the present invention, and furthermore, this solubility tends to decrease over time. is also remarkable. In the amorphous carbonate intermediate according to the invention, the carbonate wires appear to be bonded to the aluminum hydroxide in a manner different from the original alkali carbonate.

In other words, this fact indicates that even when an amorphous carbonate intermediate is repeatedly washed, the carbonate radicals are hardly reduced, or even if they are reduced, only the carbonate radicals corresponding to the adhering sodium carbonate content are reduced. confirmed by a decrease in The amount of carbonate radicals contained in the amorphous carbonate intermediate varies depending on the pH at the time of neutralization. When neutralized at pH 8.5, the intermediate contains the most carbonate radicals, It is observed that as the pH moves from this value towards pH 6.5 or pH 9.8, the content of carbonate radicals decreases. As a method for producing a basic aluminum chloride salt similar to the present invention, Japanese Patent Publication No. 45-38121 discloses that an alkaline aluminate solution is exposed to a circulating light in a carbon dioxide gas stream to rapidly react.
It is disclosed that the precipitated fine aluminum hydroxide is dissolved in an acid solution to form a basic aluminum salt.

In this method as well, alkali carbonate is certainly formed in the solution, and the aluminum hydroxide produced also contains carbonate radicals, but in this method, as the pH of the solution drops to about 10.2, However, it is difficult to keep the pH within the range of 6.5 to 9.8. Furthermore, the aluminum hydroxide produced has at most 0.09 mol of carbonate radicals per 203 A. Thus, it will be understood that the aluminum hydroxide formed by this method has undergone considerable polymerization and still has problems to be improved in terms of its solubility and its tendency to decrease over time. On the other hand, according to the present invention, aluminum hydroxide with a high carbonate radical content is formed by performing neutralization in the pH range of 6.5 to 9.8, thereby suppressing the polymerization of aluminum hydroxide. hand,
This success was achieved by increasing the solubility in hydrochloric acid and eliminating the decrease in solubility over time.

Figure 1 of the attached drawings is a diagram showing the relationship between the pH at the time of neutralization and the concentration of carbonate groups in aluminum hydroxide containing amorphous carbonate groups, and shows that the pH at the time of neutralization has a critical effect on the concentration of carbonate groups. It becomes obvious that the

In the neutralization step of the present invention, the amount of alkali carbonate added to the aqueous medium is at least equal to the amount of carbonate radicals to be contained in the amorphous carbonate intermediate, and is generally per 2031 moles of A of the soluble aluminum salt. , Na2C03
It is desirable to use it in an amount of 0.1 mol or more, especially 0.2 mol or more.

On the other hand, the starting aluminum salt is preferably used as A203 in the reaction medium at a concentration of 1 to 80 m/m, particularly 10 to 50 m/m. Although room temperature is sufficient for neutralization, the reaction may be carried out with heating if desired. However, in a reaction at a high temperature, carbon dioxide gas may escape out of the reaction system, so heating should be done at a temperature of 8,000 ℃ or less. Mixing during the neutralization reaction also requires consideration to prevent carbon dioxide from escaping.

Thus, it is possible to first fill a reactor with an alkaline substance whose pH is within the range of the present invention, and then add an acidic substance to the reactor while crossing the ocean, or to add an acidic substance to an aqueous medium having a pH within the above-mentioned range. It is possible to adopt a method of worshiping the alkaline substance and alkaline substance at the same time. In the present invention, the pH during the reaction of 6.5 to 9.8 means that the pH in the system from the start of the reaction to the end of the reaction is substantially maintained at 6.5 to 9.8. For this purpose, a method is preferably adopted in which an acidic raw material and an alkaline raw material are simultaneously added to the aqueous soot as shown in the examples described later. Reaction within this pH range effectively fixes carbonate radicals in the intermediate, imparting excellent solubility. It will be obvious to those skilled in the art that when a reaction is carried out while adding an alkaline raw material to an acidic raw material, carbon dioxide gas is liberated, making it difficult to fix carbonate radicals.
In this way, an amorphous carbonate intermediate is obtained in the form of a precipitate, which is filtered, washed with water if necessary, and applied to the next step of dissolving in hydrochloric acid.

The amorphous carbonate intermediate according to the present invention has outstanding solubility in hydrochloric acid, and the solubility of this intermediate does not decrease even when stored for a long period of time.

This intermediate can thus be supplied to the end use site in solid form for convenient transportation, where it can be dissolved and used as a flocculant, etc. In this dissolution step, the amorphous carbonate intermediate is dissolved in concentrated acid of hydrochloric acid or hydrochloric acid-sulfuric acid to obtain the formula N2(OH)X・CIy・(S○,)
Z Here, x, y and z are x + y + Z: 6, x is a number from 2.7 to 5, especially a number from 2.7 to 3.9 z is a number from 0 to 0.65, especially 0.2 The basic aluminum chloride has a composition satisfying a number of 0.4 to 0.4.

According to the present invention, by using the amorphous carbonate intermediate described above, even when the basicity curve defined by the formula (6-y・Z)X100=B is as high as 45 to 84%, It is a remarkable advantage that a liquid basic aluminum chloride flocculant which is extremely stable and has high flocculating performance can be obtained.

The liquid flocculant can be used in end applications at high concentrations of 10 to 25% by weight, and can also be used in similar applications at dilute concentrations of 0.01 to 1% by weight. The present invention will be explained in more detail below with reference to Examples.

The component measurement method and agglutination test method (jar test method) in Examples are as follows. (1) Component measurement method Among the components, N203 was measured by a general chelate titration method, and C02 content was measured by a Schrötter (alkali meter).

■ Agglutination test method (jar test method) Sample 500 samples of test water (raw water) and dilute each sample solution with water (0.105 (W/V)% as N203).
After injecting a quantity equivalent to 3.1 times as N203 (diluted to a concentration of Observe with the naked eye, and after waiting for 1 minute, take a sample of the liquid from about 2 skins below the water surface and measure the turbidity and pH.

The size of flocs was displayed according to the following standards. Large Large 5 side front and rear large 3-5 skin medium 2-3 sail small 1 Yanagi front and rear pole 4. 0.5 side or less Example 1 Aluminum sulfate (18 hydrate, reagent grade) 3,557 yen was dissolved in water. The solution made by dissolving 1,005 ml of sodium carbonate (first grade reagent) in water and the solution made by 6 ml by dissolving 1,005 ml of sodium carbonate (first class reagent) in water were poured into a container containing 10 ml of water in advance, while at the same time at the same speed. The mixture is then heated, and even after the aging process is finished, the mixture is continued for 30 minutes to undergo a ripening reaction.

The pH after the reaction was 7.6. When this is heated and washed with water, AI203: 17.75%, Na20: 0.07%
,S. 3: 0.03%, C.

1,620 pieces of carbonate composite aluminium hydroxide cake containing 2:5.50% (CO2 content: 0.719 mol relative to 2031 mol of Al) were obtained.

Next, put 797 g of 35% hydrochloric acid in another container, add the entire amount of this cake and stir it gently, it will immediately start to melt while generating bubbles and heat.Heating it further to 80-85o0 and continuing to stir it. It will completely dissolve in about 15 minutes.

Furthermore, by continuing heating and heating, water is evaporated and concentrated, reducing the total liquid volume to 1. 98th evening.
To the resulting solution, 941 liters of a 12.6% aqueous sodium sulfate solution was further added under the frame to obtain 2,739 liters of a basic aluminum chloride aqueous solution having the following composition.
Compositional formula of basic aluminum chloride: N2(〇H)3.3CI2.1(S.

4)〇. Basicity: 55% N203 concentration in aqueous solution: 10.50% The aluminum hydroxide containing carbonate plates obtained in this example has excellent solubility in hydrochloric acid, and furthermore, the obtained basic aluminum chloride aqueous solution can be used for a long period of time. The stability upon storage (6 months or more) was also extremely high.

Table 1 shows the performance test results of the basic aluminum chloride aqueous solution obtained in this example as a flocculant.

Example 2 Sodium aluminate (N203 18.69%, Na20
17.96%) 1,355 mm and sodium carbonate (reagent grade 1) 235 mm dissolved in water to make 4.09 mm and aluminum chloride (hexahydrate, reagent grade) 976 mm dissolved in water The resulting liquid was poured into a container containing 6.82 hours of water in advance at the same speed while pouring the rice porridge at the same time, and the foundation was continued for 30 minutes even after the cooking was completed. Do the following.

The pH after the reaction was 9.2. When this is filtered through a furnace, washed with water, and air dried, Al203:48.45%, Na20:0
．． 920 carbonate-containing aluminum hydroxide cakes containing 14% and 7.96% CO2 (CO2 content: 0.38 mol relative to 2031 mol of AI) were obtained. Next, put 35% hydrochloric acid 906 in another container, add the whole amount of this cake and stir it gently, it will immediately start to melt while generating bubbles and heat, and when heated further to 85-90oC, the cake will melt for about 15 minutes. It completely dissolved and became colorless and transparent.

By separating 1,000 ml of the solution and adding 1,324 ml of a 7.70% sodium sulfate aqueous solution,
An aqueous solution of basic aluminum chloride with the following composition 2,32
I got 4 nights. Compositional formula of basic aluminum chloride: N2(〇H)M2CI1,38(S.

4) Sails.

Basicity: 67% N203 concentration in aqueous solution: 10.05% The carbonate radical-containing aluminum hydroxide obtained in this example hardly loses the carbonate radicals even when air-dried, and has extremely high solubility in hydrochloric acid. Concentration was not necessary because the concentration of the solution was high.

Furthermore, the stability of the obtained basic aluminum chloride aqueous solution during long-term storage (6 months or more) was also extremely high. Table 1 shows the performance test results of the basic aluminum chloride aqueous solution obtained in this example as a flocculant.

Example 3 Basic aluminum chloride aqueous solution obtained in Example 2 before addition of sodium sulfate aqueous solution
The mixture was heated to 500 ℃ to evaporate most of the moisture, concentrated and solidified to obtain solid basic aluminum chloride 321 with a concentration of 338.04%.

When 842 ml of a 6.06% sodium sulfate aqueous solution was added to this solid, 1,163 ml of a basic aluminum chloride aqueous solution having the following composition was obtained. Compositional formula of basic aluminum chloride: Nail 2 (OH) 4. .

2CI,. 38 (S04).

．． 3. Basicity: 67% AI203 concentration in aqueous solution: 10.
05% The solid basic aluminum chloride obtained in this example is stable even during semi-permanent storage and is extremely easily dissolved in water or aqueous sodium sulfate solution (for addition of sulfuric acid). It has the advantage that it can be stored or transported in a solid state and immediately dissolved and liquefied as needed.

Further, the stability of the basic aluminum chloride aqueous solution obtained by the final dissolution during long-term storage (6 months or more) was also extremely high. Table 1 shows the performance test results of the basic aluminum chloride aqueous solutions obtained in Examples as flocculants.

The comparative examples listed in Table 1 are examples in which commercially available basic aluminum chloride (PAC) was used as a flocculant.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the generated pH (pH at the time of neutralization) and the C02 content of amorphous carbonate radical-containing aluminum hydroxide obtained by the process of the present invention.
The content (C02/mountain 203 mole fraction) and the horizontal axis indicate pH. Figure 1

Claims (1)

[Claims] 1. Neutralize a soluble aluminum salt in an aqueous medium containing an alkali carbonate so that the pH during the reaction is 6.5 to 9.8, so that the molar ratio of CO_2/Al_2O_3 is 0.1. The process of producing the above amorphous carbonate radical-containing aluminum hydroxide, and dissolving the amorphous carbonate radical-containing aluminum hydroxide in hydrochloric acid or a mixed acid of hydrochloric acid and sulfuric acid, yielding the formula Al_
2(OH)_x・Cl_y(SO_4)_zIn the formula, x,
y and z are x+y+2z=6, x is a number from 2.7 to 5, and z is a number satisfying a number from 0 to 0.65. Process for producing basic aluminum chloride salt. 2 the soluble aluminum salt is aluminum sulfate;
The manufacturing method according to claim 1, wherein neutralization is carried out using an alkali carbonate or a combination of an alkali carbonate and another alkali. 3. The manufacturing method according to claim 1, wherein the soluble aluminum salt is an alkali aluminate, and neutralization is performed using a mineral acid. 4. The manufacturing method according to claim 1, wherein a combination of aluminum sulfate and alkali aluminate is used as the soluble aluminum salt, and neutralization is performed by mixing the two. 5. The manufacturing method according to claim 1, characterized in that an amorphous carbonate radical-containing aluminum hydroxide having a CO_2/Al_2O_3 molar ratio of 0.2 or more is produced.